Preparation of solutions



July 23, 1946. R. c. HouTz PREPARATION OF SOLUTIONS Filed Nov. 4, 1944 H l l m KY Patented July 23, 1946 UNITED STATES PATENT OFFICE PREPARATION F SOLUTIONS Bay Glyde Hauts, Snyder, N. Y., assigner to E. I. du Pont de Nemours 0cm Wilmington. Del., a corporation of Delaware Application November 4, 1944, Serial No. 562,015

(Cl. 26o-32) 15Claims.

This invention relates to a new composition oi' matter and shaped articles produced therefrom. More particularly. this invention relates to an organic solvent solution of polyacrylonitrile, i. e. polymerlzed acrylonitrlle or polymerized vinyl cyanide (CHFCHCN) s, and copolymers and interpolymers of acrylonitrile in which at least 85 by weight of the polymer is acrylonitrile, and to the production of shaped articles from said organic solvent solution of said polymers of acrylonitrile.

This application is a continuation-impart of the copending application of Ray Clyde Houtz, Serial No. 447,446, led June ll', 1942.

Polyacrylonltrile and copolymers and interpolymers of acrylonitrile with other polymerizable substances, for example vinyl or acrylic compounds, in which at least 85% by weight of the polymer is acrylonitrile have been known for some time and recognized as possessing desirable physical and chemical properties including toughness and insoiubility in and insensitivity to common organic solvents such as methyl or ethyl alcohol, acetone. ethyl ether, ethyl acetate, hydrocarbon solvents, chlorinated hydrocarbons and the like. Because of these facts, numerous attempts-have been made to form these polymeric materials into yarns. iilms and other shaped articles.

The copending application of George H. Latham, Serial No. 562,012, filed of even date herewith disclom solutions of polyacrylonitrlle in dimethyl carbamyl compounds and the production of extruded and otherwise shaped articles and structures from such solutions. The abovesaid application of George H. Latham represents the first succesiul dissolution of polyacrylonitrile in a solvent to produce a solution which is suitable for the production of commercially useful textile yarns or wrapping tissue films and similar tough, nexible struc The present application relates to a similarly satisfactory dissolution of polyacrylonitrile in an organic solvent taken from a diiierent class of organic compounds and the polyacrylonitrlle solutions produced thereby are similarly satisfactory for the production of tough, flexible, dense, colorless yarns and mms which are suitable for use in practically all general commercial applications of such products.

It has been known heretofore that concentrated aqueous solutions of inorganic salts such as lithium bromide, zinc chloride and sodium sulfocyanide will dissolve polyacryionitrile and it has been proposed (Bein U. B. Patent No. 2,140,921)

to employ the resulting solutions in the formation of yarns and films. However. it has been found substantially impossible to use the resulting compositions insuch a manner. Their extrusion into coagulating baths of the type proposed (including such non-solvents for acrylonltrile as water, dilute acid, dilute salt solutions. etc.) result in the formation of shaped articles that contain large amounts of the inorganic salt of the proposed solvent. These salts are distributed throughout the structure and destroy the continuity of the polyacrylonitrile phase and the structure poor physical properties. Removal of these salts. when possible, results in the formation of a porous, spongy, weak, undesirable structure that is very brittle and completely unsalted for use as a yarn or nlm. Moreover, when it is attempted to form a multi-mament yarn by extruding, for example the proposed aqueous sodium sulfocyanlde polyacrylonitrile composition, into a dilute acid bath, it is found that the individual filaments obtained stick together to form an essentially monolament structure that is extremely brittle and cannot be bent or worked without breaklns.

U. S. Patent No. 2,167,537 to Tobls points out that certain copolymers of acrylonitrile and an acrylic acid ester (those copolymers containing not more than of acrylonitrile) are soluble in mixtures of organic solvents such es dioxan, monochlorbenzene, cyclohexanone, etc. However, thesc liquids are incapable of dissolving or even swelling poiyacrylonltrile or copolymers of acrylonitrile containing higher percentages of aorylonitrile, i. e. acrylonitrlle polymers of the type with which this invention is concerned. As previously mentioned, polymers containing such high percentages (at least 65% by weight) of acrylonitrile are especially desirable for use because of their good physical properties and excellent chemical resistance.

It has also been proposed (Rein U. S. Patent No. 2,117,210) to dissolve polyacrylonitrile in molten Quaternary ammonium salts such as benzyl pyridinium chloride, an ionisable salt. Although the resulting solution can allegedly be used to form yarns or iilms oi polyacrylonitrlle, the solution itself is dark red to brown in color. indicating that some decomposition of the polyacrylonltrile or some reaction between the polyacrylonitrile and the molten salt has probably taken piace. Such solutions are not satisfactory for the production of commercially useful, shaped articles of polyacrylonitrile. Here again, it has been found practically impossible to obtain lilamentary structures such as yarns from the composition` Hlms or illaments, when obtainable, are extremely brittle: they are highly colored and very weak. because of the presence within them of residual quaternary ammonium salt. Removal of this salt is dlmcult and the resulting structures contain numerous and large voids that make the structures substantially useless for commercial 12111110688.

It is therefore an object of this invention to dissolve polyacrylmitrile or a. copolymer or interpolymer o1' acryionitrile in which at least 85% by weight oi' the polymer is acrylonitrile. in a solvent which does not react with or decompose the polymer and which may be substantially ccmpletely removed from the structures formed of suchasolution.

It is another object of this invention to produce a solution of polyacrylonitrile or a copolymer or lnterpolymer of acrylonitrile in which at least 85% by weight oi' the polymer is acrylonitrile, in a solvent which does not react with or decompose the polymer, the solution being suitable for the formation of commercially useful, void free articles of polyacrylonitrile. for example yarns which are suitable as textile yarns and lllxns which are suitable as mapping tissue.

It is another object of this invention to produce a solution of polyacrylonitrile or a copolymer or interpolymer of acrylonltrile in which at least 85% by weight ci the polymer is acrylonttrile, in a volatile organic solvent. which solution isstahleoverextendedperlodsoftimeandis eminently suited for use in the manufacture oi' shaped articles such as yarns, mms, tubes, straws, artificial horsehalr. bristles and ribbons. or when highly concentrated, for use in the manufacture oi molded articles.

It is a still further object of this invention to produce shaped articles and structures ci polyacrylonitrile or copolymers or interpolymers of acrylonitrile in which at least 85% by weight of the polymer is acrylonitrile.

It is still another object oi this invention to produce a shaped article or structure oi' polyacrylonitrile or copolymers or interpolymers of acrylonitrlie in which at least 85% by weight of the polymer is acrylonitrile, for example a yarn. nlm, tube, bristle or the like which is tough` ilexible, tenacious and free from voids.

Other objects of the invention will appear hereinafter.

'I'he objects oi' the invention may be accomplished in general by dissolving polyacrylonitrile, or a copolymer or interpolymer oi' acrylonitrile in which at least 85% by weight of the polymer is acrylonitrile in a compound containing a sulfoxy methylene group (in which vsulfoxy is as donned in Patent Oillce Classiiication Bulletin 74, page 30) and which compound is not a sait, for example dimethyl nili'oxide.

Ii' the solvent has a relatively low boiling point (less than about 250 C.) the solution of acrylonitrile polymer may then be formed into a shaped structure, for example a yarn or iilm, and the solvent removed from the shaped structure to coagulate the saine. When the solvent is relatively non-volatile and has a boiling point of about 300 C. or more. shaped articles may be madeiromthesolutionandatleastaportionof the solvent may be retained therein as a plasticiser for the articles.

Ithasbeeninrecentyearsthat under certain conditions. an atom of hydrogen is attracted by rather strong forces to two atoms insteadofonlyone, sothatitmaybc considered lll 4 to be acting as s bond between them. This is called the hydrogen bond.

The dimculty of dissolving polymers containing at least by weight of acrylonitrile is due to the presence within the polymer molecules oi' strong hydrogen bonding forces. and in order to dissolve one of these polymers, it is n to und. a material which will undergo hydrogen bonding with the active hydrogen bonding groups of the polymer molecules and thus weaken the strong hydrogen bond within the polymer molecule and cause the hydrogen bonding forces to be shared between molecules of the polymer and the solvent. In this manner. it is possible to form a molecular dispersion of the polymer within the solvent and thus form a solution.

However. the strength of the hydrogen bonding capacity cannot be taken as the sole criterion as to whether or not a cnpound will function to dissolve an acrylonitriie polymer. It is also necessary that in order to function as s solvent for an acrylonitrile polymer, the compound contain certain groups which will be capable of satisi'actorily sharing a hydrogen bonding force with the particular active group of the acrylonitriie polymer. In most instances. the groups require the presence of a hydrogen atom on a carbon atom to which the active group ls attached (designated as an alpha-hydrogen atom). Buch active groups as require the alpha-hydrogen atom are ineilective to impart solvent power ii the alpha-hydrogen atom is It has now been found that groups capable of conferring solvent power include dimethyl carbamyl Citi- [Ca (Bl-N0 yano (-CEN), thiocyano (-B-Cs) and sulfgroups. provided however that the cyano. thiocyano and suli'oxy groups require attachment (through their unsatisfied carbon and sulfur valences) to a carbon atom which is in turn attached to at least one hydrogen atom (alphahydrogen) in order to render them eil'ective. The dimethyl carbamyl and the formyl imido groups are eil'ective in the absence oi' the alphahydrogen atom. (It is possible that they contain the equivalent oi' an alpha-hydrogen atom within their own structures.) Thus, the groups dimethyl carbamyl iormyl lmido (HCON cyanomethylene CHCN), thiocyanomethylene CHSCN) and sulfoxymcthylene CHSO. CHSO=-. CHSOO, and CHSGa0-l shall hereinafter be referred to as solvogenic groups and compounds containing them are frequently capable of dissolving an acrylonitrile polymer containing at least 85% by weight of acrylonitrlle.

formyl imido In the event that two or more groups requiring the presence of an alpha-hydrogen atom in order to render them solvogenic are attached to the same carbon atom and compete with each other for an available alpha-hydrogen atom, the sulroxy group, the cyano group and the thiocyano group take preference over each other in the order named. to form the solvogenic group, the lower ranking group or groups present assuming merely the nature of an inert substituent on the carbon atom.

It has furthermore been found that compounds containing the above-mentioned solvogenic groups will be solvents for the abovementioned polymers only if the carbon content of the compound be within certain limits, the limits for the compounds of the present invention being given below. If the ratio o! carbon to solvogenic groupings is maintained within the said limits, the compounds will retain solvent properties of the polymer even though the molecule be of considerable size and complexity. The solvent power of the compound for acrylonltrile polymers is generally increased ii' more than one of the solvogenio groups is present in the molecular structure of the compound, the effect of these groups being additive.

It has now been found that sulfoxy methylene compounds which are fusible without decomposition and particularly those sulfoxy methylene compounds embraced by the following empirical formula and preferably having a melting point below 250 C.. will dissolve polyacrylonitrile and copolymers and interpolymers of acrylontrile in which at least 85% by weight of the polymer is acrylonitrile:

groups should equal at least the total number of any combination of said halogen, oxygen and bivalent sulfur atoms and the hydroxyl and thiol radicals, and the number of said non-solvogenic cyano, thiocyano and sulfoxy substituents not exceeding the value of m+1+u+w. The two respective tolerances for the two said groups of substituents are independent oi each other and members of both groups may be present in the molecule up to their group tolerances. The said oxygen or sulfur substituents may be present as bivalent groups either as a side group (carbonyl or thiocarbonyl) or within the chain (ether or thlether), as the case may be. It is preferred that the carbon atoms in the Ca, Cp, Cr and Co portions ot the above formula be joined to each other, hut this is not essential.

Representative compounds coming within the scope of the above formula and suitable for use as solvents for the above mentioned acrylonitrlle polymers include:

CHIiBOlCHI Methane dlsulonic acid, dimethyl ester CsHsSOlCHeCHsSOICxHs Ethanel,2disulfonic acid. dlethyl ester CHxSCICHsCHsSOICHI Ethane-Lz-disulfonic acid, dimethyl ester 0 CHISOICHs CH(S0;CH|)3 Qfpropanone-l ,l.3tri.sulfonlo scid, trimethyl ester (CHtBOsCHa)zC=O prepararme-1 .3-disulionic acid. dimethyl estar wherein X represents the tree valence of the sulioxy group being also attached to carbon: m, q and u are integers equal to or greater than zero; w is an integer equal to or greater than 1; n, p, r and v are integers of such value than n/m is equal to or less than 1.5; p/q is equal to or less than 1.5; r/u is equal to or less than 0.5 and v/w is equal to or less than 2.

The compounds are not salts but may be cyclic or acyclc in nature and may posses one or more ethylenic or acetylenic linkages. Valences other than those contained in carbon-to-carbon linkages and not shown to be satisfied in the above empirical formula must be satisfied by a. substituent taken from the group consisting of hydrogen, halogen, oxygen, bivalent sulfur atoms or by hydroxyl, thiol, cyano, thiocyano. or sulfoxy radicals, the total number of said halogen, oxygen, bivalent sulfur. hydroxyl and thiol substituents not exceeding the sum (m-l-q-i-u-l-w), i. e. the number of O C Erg-O -C Ha C H Ethyl methane suliinate O i CHxEl-O-C Hr Methyl methane sulilnate CHaSOaC Hs Dlmethyl sultano oms olomomon Bete-hydmxyethyl methyl lullen (CHnBOnCHsCHaO nnmumznyluuonykmyl) um (CHICHJE 01h03; Bistethyllullenyl) methane CHlCBOlOHlh 1,1-bls (methylmllonyl) ethme CILCHGOIC'IHI): Lbbtsthylsulionyl) ethme CHIC (S OICaHxOHQlCIHa L12-trl: (ethyllulfonyl) preme C IHS 0101110 'lrla(ethylsul1'ony1) methane OHCNBOaCaHI Bis(ethy1sullonyl) ehloromethme C B18001011; Bla(methykn1lonyl) methane 801C Hl C HIC H S x0 IH l-methylsulfonyl-l-ethyl sullonyl athene (CBaSOaCHgSOnCEmBOa Bln(methylsulfonylmethyl-sullonylmethyl) Iuliano C He CHICHIJ: (SOICHI 2,2bis(methylsulfonyl) butano (C3010 (BOQCHm 2,2-bll(methylm1funyl) propina CHaCHaCHOnCHs): l,1hls(methyl.sul!onyl) propme (CHIS OsCBzhS Os Bls(methylsulonylmethyl) sullen (CaHaSOaC H018 Oa lsthylsulfonylmethyl) sullone i C :H53 0x C Hl) l 1,2;bie(ethylsn1!onyl) ethane CHnC (SOaCnHhC (S 0|CxHaC Ha 2,2.3,3teh'akis(ethylsnltnnyl) butano C Ha 0x C HxC Hl Methyl ethyl sullene C HIIC H (S OsCxHl) |11 1,1.3,3tetmkls (ethylsulfnnyl) propane CHxBOnGHICHxSOlCHn 1,2-bls(methylsul!onyl) ethane (CHaS0|CHx)|O=0 L15-ble (methylaulIonyD-Z-propmene CHSOCHCBIBO CH:

l,2hla(methyleulllnyl) ethnne CaBtSO CHCHxSOCxH: 1,2-bls (ethylsumnyl) ethnne C C H150 C En) l Tetnkmmethylsumnylmethyl) methane C HIC E3B O C H Methyl ethyl sulroxlde (01h80) :CH: Blsnethylsulnyl) methane C RnB 0 )1C H Cl Blumethylsulnyl) ehlorometham CHahS 0 Dimethyl lulloxide NCB-05011180503: 2thlooyenoethmemllente acid, methyl Itter NCS-CHN'JEBrBOxCHa NO-ClxCHaSOsCHI 2-cyanoethsneeulfonle wld, methyl ester N C-CHICHBrBOaCHe l-bromo-Z-cylnoethnnesulfonle acid, methyl ester NC-CHICHIBOaCxHi vyunoethanesullonic acid, ethyl esta:

NC-C HBrCHaS OaCzB; 2-bromo-2-eymthanesullfonic mld, ethyl eater BOKCBaSOsCHx):

Sultonyl bis(methanemlfonic wld), dimethyl ester CHxCHxSgCHlCHISOICIHI 2-(ethyllul1onyDethanesultonlu mld, ethyl alter CHaSOlCHaCBnBOaCtHI calsmcmcomonm (N,Ndlmethylearhamyl) methane-saliente wld. methyl ester CgBgSOxCHaC 0N (C El) s (NN-dimethylrbamyl) methane-summe acid. ethyl eater (N ,N -dlmethylcarbnmyh meth ena-eulfnnlc uid. n-propyl ester (CHlhCHBOaCHIC ON(CH\)| (N,Ndimethyleerbamyl) methaneeulfonio ecld. isopropyl ester CH3 (C'HSO) B80101111 1-(ethyllh1nnylj-1-(ethyl-eulfonyl) ethm CH. CH|SO (IJHSOnOHa 1-(methylaulnyD-l-(methyl eulronyl) athene CH; BOCH;

oN omsoomcmdnc omen.)- nmamnympmwmnnyuummmmm 'ir-(Betlthlocynnosthylmlnyl) butyronitrlte SCN C 5x60 CE1 BON Alpllrthlooyam-beta-(mothylmlnyl) proplmiltrlle NCB-CRnCHnCHIBO GHCElCH'CN yhhmmmnpropylsullinyl) butyronitrile cN omcmsoiomdnc Gluem). NN-almthymphmmebemmynumn'yl propionamide rSGHmN C OCBrSOxCHaCH'CHrCN y(N, -dlmothylearbanglllrllethylsulfonylybutyronl- C'HsBOgGHrCBIHC 0N(CHa)a N ,N-dlmethylalpha-cyano-y-me thylsulionyl butyramide E O N CHICHIBOICHIHCN Alphmtlileeynno-beta-ethyl-sulfonyl-proplonltrlle NCS-CHICHaCHrSOzHICHICHaCN rhthlooyanopropylsulfonyl) butyronltrlle 2-|slplls-eyano-beta(N,N-dimethyl-cerbamyl) ethylsulflnyl]- ethanesullonio acid. ethyl ester CHaCHsSOsCHaCHISO CBlCHzHC ON(C Hz):

2-I -cysn owfN N-dlmethyl-carbnmyl) propylsulllnyll- 7 ethnulronm acid, ethyl @sur CHrCHaCN CHICHsBOxCBsCHsSOHC ON(CH|)! CECHSOsCHsCHz-SOr-HCHaC ON(CH1)1 2 lla-'cyano-bete-m N-dlmethylearbamyl) ethyl-enlfonyl]- m ethanes'ulonic acid, ethyl ester Z-ITeyann-ym N-dlmethylrbamyl) propylsulonyl]- ethanesulfonic acid, ethyl ester SCN CBaCAHsSOICHaCHxSOCHaCHzHC0N(CHs)| 2-1 tlzl' moq-(MN-dlmetbyl-carbsmyl)propylsuluyll 7. my ethnneeullonlcacid, ethyl ester CON(CH1):

CHlCHxSOa-CHaCHzSOH CBgCHrSCN I1-thi ano-elphn-(N,Ndlmeth learbamyll propyl- :nyll ethanesullonlc acidy, ethyl ester CB1-s GHz-CH:

Trlmethylene sulfone CHI-CH:

Trlmethylene sulfoxlde CNCHi-CH-CHg-CH;

B O l Alpha eyanomethyl trlmethylene sullone In lieu ot the sterile groups, such as CN for example, in certain of the above typical compounds, other groups in the sterile state may be included in the molecule, e. g, SCN, sulfoxy, etc.. provided that the tolerance limits are observed as explained above.

All of these compounds are misclble in a wide range of proportions with polyacrylonitrile, and copolymers and interpolymers o! acrylonltrile and they do not appear to react with or decompose them. Many of the compounds are also miscible with (soluble in) such non-solvent liquids for the polymeric materials as water, aqueous -salt solutions, alcohol, glycerol, etc. Solutions or an acrylonitrile polymer ln many of the compounds of this invention can therefore be extruded into such liquids to form shaped articles such as yarns. lms, etc. of the polymer with the solvent being removed by selective solution in the liquid coagulant. Moreover, because many of the compounds of the invention are volatile (vaporlzable without decomposition at atmospheric pressure and at temperatures not exceeding 250 CJ, solutions of the polymer in such compounds are eminently suited for use in a dry spinning or casting process for the preparation of a yarn or lm of the polymer.

For the purpose of definition, a solvent is a material which, when in the liquid state. is capable of forming solutions in which the polymer is present in a concentration of 5% or more. In most instances, the solvent and polymer are misclble in almost all proportions although the mlsclbility may take place at elevated temperatures in the case of certain compounds.

The solutions of the invention are prepared by dissolving the polyacrylonitrile. or copolymer or interpollrmer o! acrylonitrile with one or more oi the compounds ot this invention. Some oi these compounds exist in the solid state at ordinary temperatures and dissolve or retain the polymer in clear solution only at elevated temperatures, for example at temperatures oi' 100 C, or higher, below which temperature the composition takes on the appearance oi a gel. Even in such a case however. there is usually no substantial evidence of immediate separation oi' the gel into two phases although after standing (i. e. sometimes after a period of several weeks), the gels may undergo syneresis. This phenomenon of gel formation or syneresis is reversible however and subsequent heating oi the gelled or syneresed mass causes it to revert to solution form.

In view of the relatively high melting points of some of the solvents oi' this invention, they would have comparatively little use in the production of an acrylonitrile polymer spinning or casting sointion. Such solvents are. however. excellent solvent plasticizers for acrylonitrile polymers since they are soluble in a wide range of proportions with the said polymers. The present invention, therefore, contemplates solid solutions of acrylonitrile polymers containing atleast 85% by weight or acrylonitrile as well as liquid solutions thereof,

Shaped articles obtained from solvent solutions of acrylonitrile polymer prepared in accordance with the invention and from which the solvent is subsequently removed are substantially free of foreign matter and voids alter removal oi' the solvents and the acrylonitrile polymer remains substantially undecomposed and chemically unchanged irom the original acrylonitrlle polymer prior to its solution.

The above described organic solvent solutions ,of acrylonitrile polymer may be shaped in the form of filaments, yarns. nlms. tubes and like structures by apparatus and processes generally known in the art, the detailed operating condi tions being suitably modined.

Suitable methods and apparatus for the production of shaped articles oi' the polymers of this invention will be readily apparent by reference to the following detailed description when taken in connection with the accompanying illustrations in which:

Figure l is a diagrammatic vertical sectional view showing a dry spinning cell suitable for use in accordance with the invention;

Figure 2 is a diagrammatic perspective view showing a yarn drawing device for use in connection with the invention; i

Figure 3 is a diagrammatic perspective view showing a wet spinning apparatus for use in the invention; and

Figure 4 is a diagrammatic side elevational view showing a suitable iilm casting apparatus for use in accordance with the invention.

Referring to Figure l of the drawing, reference numeral il designates a spinneret through which a plurality oi filaments I5 are formed by extruding a filament-forming solution supplied to the spinneret by means oi' conduit il. The spinning il is iacketed with a material i1 such as a reiractory in which is embedded an electrical heating coil I9. The spinning cell can thus be operated at any desired temperature. A plurality of conduits 2l are provided adjacent the bottom of the device for passing evaporative medium through the cell so as to evaporate the solvent from the extruded filaments il. The evaporative medium is removed from the cell through outlet openings 23. 'Ihe yarn comprising the plurality 16 of filaments Il is passed from the bottom of the spinning cell around lulde roller Il and is wound on a bobbin 21.

Referring to Figure 2 of the drawing. the yarn It is removed from the bobbin package 21 and passed about draw roller 2l, and separating roller l i. From draw roller 20, the yarn is passed to a second draw roller Il and separating roller il. The yarn is passed laround the two sets of draw rollers including their separating rollers a sum :lent number o! turns to prevent slippage ci the ya "n. Draw roller 3l is rotated at a greater speed, :or example three to ten times the speed or draw roller 2l. In this manner, the yarn I8 is stretched between the two draw rollers. As the yarn passes between the two draw rollers, a heating medium is brought into contact with the yarn through blower nozzles 31 and 3l. The yarn passing from the draw roller 33 is wound on bobbin 4|. The drawing or stretching oi the spun yarn as described is not claimed as part oi the present invention, but is claimed in the copending application of Daniel T. Meloon. Serial No. 496,397, filed July 28, 1943.

Figure 3 of the drawing illustrates a wet spinning apparatus for the production of yarn. The acrylonitrile polymer solution is passed through conduit ll and is extruded through spinneret Il to form a multiiilament yarn II. The yarn 54 is passed about guide roller l1 which is positioned within the coagulating liquid in tank ll. The yarn is then passed about guide roller 59 and is wound on bobbin 0I.

The organic solvent solution of the acrylonitrile polymer may be cast in the form of a iilm as illustrated in Figure 4. In accordance with this apparatus, the polymer solution is passed from hopper 1| on to the endless steel band 13 where it is smoothed by means o! a doctor knife 1B. The band, together with the illm, is passed under a means 11 for bringing a heated drying medium into contact with the nlm. The lm BI is pulled from the band 1l and collected on a mill roll 8l.

The polyacrylonitrile for use with the invention is preferably prepared by the ammonium persulfate catalyzed polymerization of monomeric acrylonitrile dissolved or emulsined in water. It can, however, be prepared by any other suitable type oi' polymerization reaction, such as. for example. the emulsion type reaction disclosed by U. S. Patent No. 2,160,054 to Bauer et al. The polymer preferably possesses a molecular weight within the range ci 15,000 to 250,000 or even higher, as calculated from viscosity measurements by the Staudinger equation:

Molecular weight- Ilfv Bviscoslty of solution N" specic ssty viscosity of solvent l and =concentration of the solution expressed as the number of moles of the monomer (calculated) per liter of solution.

The molecular weight of the polymer obtained is dependent on such factors as the concentration of the monomer in the water,' the amount and type of catalyst present, the temperature of the reaction, ete. For example, polyacrylonitrile having a molecular weight of approximately 60,000 can be prepared as follows: To 94 pounds of distilled water heated to 40 C. add 40 grams oi I ammonium persulfate catalyst and B grams of sodium bisultlte activator. Then add 16 pounds of acrylonitriie slowly lwith stirring over a period of two hours. The polyacrylonltrile having the above said molecular weight will precipitate from the solution. Increasing or decreasing the amount oi the catalyst, while maintaining the other conditions constant, decreases or increases the molecular weight of the polymer. Acrylonltrile copolymers containing at least 85% by weight Aof acrylonitrile and likewise preferably possessing a molecular weight oi 15,000 to 250.000 or higher can be prepared in a similar manner.

The following examples in which parts, proportions and percentages are by Weight unless otherwise specified illustrate preferred methods of preparing solutions in accordance with the principles ot this invention and oi employing these solutions in the manufacture of commercially satisfactory shaped articles of the polymer. The invention is not to be limited by the details set forth in the examples.

Example I Fifteen parts of a polyacryionitrile prepared by the polymerization of monomeric acrylonitrile in accordance with the teachings of U. S. Patent No. 2,160,054 to Bauer et al. and possessing an average molecular weight of 120,000 as determined by the Staudinger equation from viscosity data are ground to an average particle size of 200 mesh and mixed with 85 parts oi dimethyl sulfoxlde, the resulting mixture being heated Within a period of fifteen minutes to a temperature of 90 C. to form a clear solution possessing a viscosity oi 100 poises at this temperature. If subsequently cooled, the solution becomes more viscous.

The solution was heated to a temperature oi 90 C., cast on to a surface heated to 90 C. and dried to form a thin, transparent film of acrylonitriie polymer, the film being tough, flexible and tear resistant. The iilm of acrylonitrile polymer remaining on the plate is then removed from the plate to yield a strong, transparent sheet of approximately 0.001 inch in thickness. YThe sheet, in addition to being flexible and resistant to tearing, is insensitive to the common volatile organic solvents. It is substantially impervious to oils, hydrocarbons and common organic substances. It is approximately sixteen times as impervious to the transmission therethrough ci moisture vapor as a sheet of regenerated cellulose of the same thickness. In addition, the sheet possesses a brilliant clearness that makes it especially desirable for commercial use. The film can, ii' desired, be stretched longitudinally and transversely to improve its strength in these directions. It is characteristic of this stretched nlm that it does not shrink greatly when subjected to elevated temperatures. For example, such a iilm, when subjected to a temperature of 175 C.. will shrink approximately 10%.

Example II Vat a temperature of 115 C. into a bath comprising glycerol heated to 115 C. to form a l-iilament yarn having a total denier of 150. A bath @travel oi' 24 inches was employed, the yarn being subiected to a tension of 0.7 gram per denier 18 (based on the final yarn denier) during its travel through the bath. The dimethyl sulfone was removed from the yarn by the glycerol, thereby coagulating the copolymer. The yarn, which possessed a tenacity of 4.0 grams per denier and an elongation of 12%, was colorless and lustrous in appearance. It accepted acid and basic dyes readily.

Example III Seventyiive (75) parts of the powdered polyacrylonitrile of Example I were intimately mixed with 25 parts of solid bis(beta methylsulfonylethyllether and heated to a temperature of 170 C. to form a viscous, homogeneous mass or solution. Subsequent cooling of this solution to room temperature resulted in the formation of a gellike mass oi high viscosity which could be molded to a strong, tough, rod-like structure.

The solution of acrylonitrile polymer dissolved in an organic solvent in accordance with this invention must be of such a concentration that its viscosity at the operating temperature is within a workable range. When it is to be employed in the spinning of yarn or the casting of nlm, the solution should preferably have a viscosity within the range of 25 to 750 poises. When the polymer has a molecular weight of 250,000 or more, this requires that the maximum concentration oi polymer in the spinning solution be of the order oi 10%. Generally, it is preferred that the spinning solution contain at least 10% of the polymer because of the difficulty of rapidly removing large amounts of solvent from the solution in the spinning operation. Moreover, it is economically undesirable to use such large amounts of solvent for the spinning of a given amount of polymer although it is true that the solvent can be completely recovered from the spinning operation and reused. For these reasons, it is preferred to employ a polymer having an average molecular weight of between 40.000 and 150.000 since such a polymer forms a solution of the desired viscosity in concentrations of the order of 15% to 25%, and at a desirable spinning temperature of the order of to 150 C. 0i course, it is within the scope of the invention to heat the solution to a higher temperature, even to above the normal boiling point of the solvent, for the actual spinning operation. Here again, the controlling factor with regard to the temperature of the spinning solution is the viscosity of the solution.

The evaporative medium employed in the dry spinning of filaments and yarns or the dry casting of illms in accordance with this invention may be any vapor inert to the fllmor filamentforming solution such as air, nitrogen, steam, etc., or any suitable mixture thereof. The temperature of the evaporative medium is dependent on such factors as the dimensions of the spinning cell, the composition and rate of extrusion of the spinning solution and the rate of ow of the evaporative medium. It is only necessary that these several factors be so correlated that the yarn or other shaped article leaving the spinning cell be sufilciently freed of the solvent so that it is solidified and capable of being wound into package form or otherwise collected.

As indicated in Example II above, shaped articles of acrylonitrile polymer can also be formed by extruding the spinning solution into a suitable precipitating bath comprising a liquid that is miscible with the solvent but is a chemically inert non-solvent for the acrylonitrile polymer.

As examples of such a liquid may be mentioned water, glycerin, organic solvents, such as alcohol, ether, etc.. or aqueous solutions of salts, alkalies or acids. The co-pending application of William W. Watkins. Serial No. 496.376, tiled July 2B, 1943, covers the use of glycerol and aqueous solutions of salts'as baths, preferably at elevated temperatures, for the wet spinning of acrylonitrile polymer yarn, from solutions of the polymer, preferably with substantial tension and stretch being applied during spinning.

The length of travel of the shaped article through the precipitating or coagulating liquid is not critical to the invention. provided only that it be suiliciently long to solidify the acrylonitrile polymer. When the precipitating bath is water. the bath travel may be as short as l/g inch, or it may be lll or more inches in length. When the precipitating liquid is an aqueous salt solution such as a solution of calcium chloride, the solidiication of the acrylonitrile polymer structure is generally more gradual than in the case of water so that it is necessary to use a somewhat longer bath travel than with water. If desired, suitable means such as guide rods or rollers may be placed in the bath to tension the yarn or other shaped article during its formation.

The article of acrylonitrile polymer thus ob` tained can advantageously be subjected to a stretching operation of the type employed in the above examples. This stretching is preferably performed by passing the yarn between two positively driven rollers, the peripheral speeds of which are so adjusted that the article is stretched to from two to ten times its original length. preferably approximately six times its original length. This stretching of the formed article may be performed at any suitable time. However, in the case of articles formed by the wet spinning or casting technique. it is preferably performed before the article has been completely dried. The orientation of the structure thus obtained greatly improved the physical properties of the structure including its tenacity, its resilience, etc.

This stretching of the shaped arti le can also be accomplished by causing the article, while passing between stretching rollers, to contact a heated stationary pin, or to pass through an inert medium such as air, water, glycerin, etc., heated to a high temperature. Obviously, the article must not be exposed to this high temperature for a period sufficiently long to decompose the polymer. In general however, the time of contact of the article with the heated medium is so short that temperatures up to 250 C. can be employed. Although it is generally preferred to heat the article to a temperature of at least 100 C. during the stretching operation, this is not essential. Desirable results can be obtained by stretching the article without the application of heat, for example by stretching at room temperature.

In addition to acting as solvents for polyacrylonitrile. or copolymers or interpolymers of acrylonitrile, the sulfur-containing compounds of this invention, when present in small amounts, can also be used as plasticizing agents for the polymer and the higher boiling compounds of the invention are especially suited for such use. At the same time, it is, of course, to be understood that non-solvent softeners such as glycerol, etc., can also be incorporated in the solutions of this invention. these materials remaining in the subsequently formed articles to impart a softening eiect. If it is desired to use such plasticizing or 20 softening agents with poiyacrylonitrlle. they are preferably added in the desired amount to an already formed solution of the polymer in a lower boiling solvent, for example to a solution o! the polymer in dimethyl suli'oxide.

Although the discussion thus far has been directed mainly toward the manufacture of yarns and illms of acrylonitrile polymer, the solutions provided by the invention and the evaporative and wet spinning processes described above are equally well adapted for' use in the manufacture of other shaped articles of acrylonitrile polymer such as articial horsehair, straws, bristles, tubes, bands and ribbons. For example, the solutions may be extruded through a suitable die and into a heated atmosphere or precipitating bath to form a tubular structure. or they may be extruded in any other desired manner. Moreover. because the solvents of the invention are miscible in a wide range of proportions with acrylonitrile polymer, the powdered polymers may be treated with small amounts of the solvent to yield a substance suitable for use in the formation of molded articles. This is a particularly important result inasmuch as it has heretofore been difiicult to use this material in molding operations. In this same manner. a plurality of sheets of acrylonitrile polymer may be treated with small amounts oi' solvents and Dressed together to form laminated articles. When present in the shaped article, the solvents of this invention (particularly those of high boiling point) are excellent plasticizers. Of course, the shaped articles may also be treated with non-solvent softening agents. for example glycerol. These plasticizing and softening agents may be incorporated in the solution of this invention or they may be applied to the shaped article as an after-treatment; or they may be added to the acrylonitrile polymer by a milling operation wherein the agents and polymers are worked between rotating rollers until a mass of the desired consistency is obtained.

This invention is primarily concerned with the steps oi' dissolving acrylonitrile polymers in a suitable solvent to form a stable solution adapted for use in the manufacture of shaped articles. It is characteristic of the invention that the solutions provided by it are stable; the solvents do not cause a decomposition or chemical alteration of the dissolved acrylonitrile polymer. At the same time, it is also characteristic that the solvents provided by the invention are also useful in the dissolving of mixtures of acrylonitrile polymer and adjuvants such as dye modifiers, linear polyamides such as nylon, derivatives of cellulose including cellulose ethers and esters, polymers of vinyl compounds such as vinyl chloride, vinyl acetate, acrylic acid, etc., which adjuvants may be incorporated in the acrylonitrile polymer solution to modify the properties. both chemical and physical, of the resulting shaped articles.

Although this invention has been described with particular regard to polyacrylonitrile, i. e. polymerized vinyl cyanide. the solvents and processes of this invention are equally useful in forming clear, stable solutions oi such acrylonitrile copolymers and interpolymers as were considered heretofore to be insoluble in volatile organic solvents, i. e. acrylonitrile copolymers and interpolymers containing at least by weight of acrylonitrile; such solutions can be used in the same way and for the same purposes as described herein with respect to polyacrlyonitrile. It is therefore considered to be within the scope of this invention to dissolve in the above mentioned solvents copolymers and inter-polymers in which acrylonitrile is copolymerized or interpolymerized with polymerizable substances such as, for example, compounds containing one or more ethylenic linkages, e. g. vinyl acetate, vinyl chloride, acrylic acid and its esters and homologues, styrene, isobutylene and butadiene, as well as other vinyl and acrylic compounds, other olenic or diolefinic hydrocarbons, etc. and polymers of such substances. 'Ihe solvents of the present invention will also be useful as new solvents for acrylonitrile polymers which have less than 85% by weight of acrylonitrile and especially those having an average molecular weight of 15,000 to 250,000 as determined by viscosity data using the Staudinger equation and intended particularly for use in the manufacture of yarns and films.

The invention also provides a class of materials that is eminently suited for use in plasticizing structures comprising the acrylonitrile polymers. The materials provided by this invention are apparently true solvents for the above mentioned acrylonitrile polymers. They do not tend to react with or decompose the polymer, the polymeric material obtained from the solution oi' this invention apparently being of the same identical chemical composition as the initial polymer. Thus, the solvents and solutions of acrylonitrile polymer provided by this invention Y when used in relatively small amounts are capable oi softening and moistening solid particles of polymers of acrylonitrile having at least 85% by weight of acrylonitrile, whereby it is possible to form molded articles of acrylonitrile polymer. Such a process is especially adapted to the formation of laminated structures from films of polyacrylonitrile, or even from lms of other substances.

The invention provides practical methods for preparing shaped articles of polymers of acrylonitrile having at least 85% by weight of acrylonitrile, which articles are characterized by desirable physical and chemical properties. For

example, the articles are resistant to the action of water and the common organic solvents. They are not ail'ected by prolonged contact with relatively concentrated solutions of sulfuric acid, or other mineral acid, nor are they ailected by dry cleaning solvents. etc. They diier from articles of other polymerized vinyl compounds. such as polymerized vinyl chloride, in that they do not shrink greatly when heated to high temperatures. They possess a desirable high dielectric strength and are not harmed by prolonged exposure to ultraviolet light. They are also very 'resistant to the action of mold and bacteria growth.

Yarns, films and similar articles oi polyacrylanitrile prepared from the solutions of this invention can be stretched to yield oriented structures that possess a high tenacity, a desirable elongation, and a high elastic recovery that compares favorably with that oi' silk. The articles are not contaminated with undesirable salts and they are substantially free of void spaces. The films, tubings and similarly shaped articles are approximately sixteen times as impervious to the transmission of moisture vapor as are films, tubings, etc. of regenerated cellulose of the same thickness. They are substantially impervious to oils and hydrocarbons including aviation gasolines.

Because of these several unique properties which may be combined here in a single substance, acrylonitrile polymerarticles produced in accordance with the principles of this invention find many important uses. While yarns made from these polymers are capable of use wherever yarns have previously been used with more or less advantage. there are certain fields where the properties of the polymer especially commend them. For example, the high tenacity, flexibility and resilience of the yarns of the invention make them suitable for use in the manufacture of hosiery and other articles oi' clothing while the resistance to soiling and ease of cleaning (common cleaning agents may be used on them without danger) make them desirable for use in flat fabrics and either as multiiilament or monofilament yarns in the manufacture of pile fabrics including velvets, plushes. upholstery or carpeting. The yarns can be advantageously used as either the pile and/or backing of such fabrics. At the same time, their low water absorption, high resistance to mold and bacteria growth and pronounced resistance to ultra-Y violet light make the yarns highly suited for use in outdoor fabrics such as tents, awnings, tarpaulins, flags, sails and the like. These same factors, taken together with the low density of the yarn (specific gravity of 1.16 as compared with 1.52 for cellulose), also permit the yarns to Vbe manufactured into clothing and other articles for use in tropical climates where light weight, flexible fabrics that resist the action of weather, direct sunlight and mold growth are required. Other uses based on these same and related properties include the manufacture of the yarns into fishing lines, fish nets, cordage especially for marine purposes, bathing suits, umbrellas and the like. It is, of course, to be understood that the yarns of the invention can be employed in these uses in the form of either continuous laments or as staple fibers of any given length. They can be formed into novelty yarns with other fibers, both natural and synthetic in character, and because of their high resilience, the staple fibers of the invention. particularly when crimped, are highly suited for admixture with wool.

Still other uses, particularly for mcnofilamentary structures of the polymer, include the manufacture of rattan-like fabric for furniture, bristles and window screening wherein the light weight, low water absorption and high resistance of the polymer to ultra-violet light, sulfur fumes and salt air are important attributes. Moreover, the high flexibility and durability of such structures enable screens made oi' them to be rolled up when not in use. thus permitting their incorporation as an integral part of the window structure.

As previously mentioned, the acrylonitrile polymers with which this invention is concerned are highly resistant to the action of acids and most other chemical reagents including oils, greases and the like and this fact, taken together with their high softening point and controlled shrinkage, makes yarns of the polymer highly useful in industrial applications including such uses as filter cloths, covers for rayon spinning bobbins and cakes, clothing for workers in areas where acids and other corrosive fumes are present and the like. Still another important use, dependent mainly on its .resistance to acids, comprises the manufacture of the yarn or other shaped articles of the polymer including films and tubings into liners, separators or other protective parts for storage batteries, particularly of the heavy duty im. Y

The above uses are primarily concerned with f yarns (either multilamentary or monoillamentary in character) of the polymer. However, it will be understood that the same desirable properties (also present in other shaped articles of s the polymer such as film, tubing and the like) make these other articles useful in similar applications such as the protection of objects from the eiiects of moisture. common organic solvents and chemical reagents and as containers or tubing for lu the packaging or transport o! liquids including corrosive liquids, oils, greases and the like. Moreover, because of their clarity and brilliance. illms group consisting oi hydrogen, halogen. oxygen, bivalent sulfur, hydroxyl, thiol. cyano, thiocyano and sulioxy; the total number I said halogen, oxygen, sulfur, hydroxyl and thiol substituents not exceeding the sum im-l-q-l-u-i-w) and the4 o! an acrylonitrile polymer prepared in accordance with this invention also nd an important 2o use in the decorative art.

The solutions prepared in accordance with the presentinvention are also suited tor use as lacquers or coating compositions and are especially suitable for use in the coating of wire and electrical parts where the high chemical and electrical resistance oi the polymer is important.

Reference, throughout the specification and claims, to acrylonitrile polymers, polymers oi.'

acrylonitrile, and copolymers `and interpolymers oi acrylonitrile containing atleast 85% by weight of acrylonitrile" sigriles polymers containing in their molecules at least 85% by weight'oi theacrylonitrile unit which is considered to be press ent in the polymer molecule as the group the invention is not to be limited to the details 5 described herein except as set forth in the appended claims.

I claim:

l. As a new composition of matter, a polymer oi acrylonitrile containing in the polymer molecule 5o at least 85% by weight of acrylonitrile and a compound embraced by the formula:

wherein X represents a member oi the class consisting of o Il the free valence oi the suli'oxy group being also attached to carbon; m, q and u are integers at least equal to zero; w is an integer at least equal to 1; 1i. P, r and v are integers of such value that n/m does not exceed 1.5; p/q does not exceed 1.5; r/u does not exceed 0.5 and v/w does not exceed 2; all valences of said compound other than those contained in carbon-to-carbon linkages and not shown as satised in the formula being satisfied by a substituent taken from the 5 group consisting of hydrogen. halogen, Olufsen.

bivalent sulfur, hydroxyl, thiol, cyano, thiocyano and sulfoxy: the total number of said halogen, oxygen, sulfur, hydroxyl and thiol substituents not exceeding the sum fm-l-q-i-u-l-w) and the number of cyano. thiocyane and sulfoxy groups not exceeding the sum (m-i-q-l-iH-w).

3. A new composition of matter as dened in claim 2 in which the polymer iii polyacrylonitrile.

4. A new composition oi matter as defined in claim 2 in which the polymer has a molecular weight ot between 15.000 and 250,000.

5. A new composition of matter as deiined in claim 2 in which the polymer has a molecular weight of between 40,000 and 150,000.

6. A new composition of matter as defined in claim 2 in which the polymer solution has a viscosity within the range 25 to 750 poises.

[C.(.slcilssllcilsnltx.

wherein Xrepresents a. member ci' the class oono sisting of (Il CHS- u/m does not exceed 1.5; p/q does not exceed 1.5; r/u. does not exceed 0.5 and v/w does not exceed 2; all valences oi said compound other than those contained in carbon-to-carbon linkases and not shown as satisiled in the formula being satisiied by a substituent taken trom the 7l 7. As a new composition ot matter, a polymer o! acrylonitrile containing in the polymer molecule at least by weight of acrylonitrile dissolved in dimethyl suli'oxide.

8. As a new composition of matter, a polymer oi' acrylonitrile containing in the polymer molecule at least 85% by weight of acrylonitrile dissolved in beta hydroxyethylmethyl sulfone.

9. As a new composition of matter, a polymer of acryionitrile containing in the polymer molecule at least 85% by weight of acrylonitrile dissolved in dimethyl sulione,

10. The composition ot claim 2 in which the solution contains at least 10% of said Polymer of acrylonitrlle.

11. The composition o! claim 2 in which the polymer is polyacrylonitriie having a molecular 14. The composition oi claim 0 in which the weight ot between 15,000 and 250,000. polymer is poiyacryionitrile.

12. The composition of claim 2 in which the i5. The composition oi claim 9 in which the polymer is poiyacrylonitrile having a molecular polymerispolyacrylonitrile. weight o! between 40,000 and 150,000. 5

13. The composition of claim 7 in which the RAY CLYDE HOUTZ. polymer is polyacrylonitrile.

Certificate of Correction Patent No. 2,404,717. July 23,1946. .RAY CLYDE HOUTZ It is hereby certied that errors appear in the rinted specification of the above numbered patent requiring correction es follows: Co umn 4, line 46, for (-S-C EY read (-S- CEN) column 11, lines 4 and 5, strike out the formula and insert instead the following BCN column 20, line 73, for polyacrlyonitrile read polyacrylonitre; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 15th day of October, A. D. 1946.

LESLIE FRAZER.

First Assistant Commissioner of Patents.

polymer is polyacrylonitriie having a molecular 14. The composition oi claim 0 in which the weight ot between 15,000 and 250,000. polymer is poiyacryionitrile.

12. The composition of claim 2 in which the i5. The composition oi claim 9 in which the polymer is poiyacrylonitrile having a molecular polymerispolyacrylonitrile. weight o! between 40,000 and 150,000. 5

13. The composition of claim 7 in which the RAY CLYDE HOUTZ. polymer is polyacrylonitrile.

Certificate of Correction Patent No. 2,404,717. July 23,1946. .RAY CLYDE HOUTZ It is hereby certied that errors appear in the rinted specification of the above numbered patent requiring correction es follows: Co umn 4, line 46, for (-S-C EY read (-S- CEN) column 11, lines 4 and 5, strike out the formula and insert instead the following BCN column 20, line 73, for polyacrlyonitrile read polyacrylonitre; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 15th day of October, A. D. 1946.

LESLIE FRAZER.

First Assistant Commissioner of Patents. 

